Ai2o3 nanorods and methods of producing same

Abstract

Aluminum oxide particles of a nanorod morphology have beneficial properties for catalysis, filtration, purification, and other uses. Disclosed herein are nanosized aluminum oxide rod-shaped particles having an average particle length of about 50 nm to about 10 μm. These nanosized aluminum oxide particles have an aspect ratio of about 12 to about 25. The aluminum oxide particles also have a BET surface area of about 10 m 2 /g to about 200 m 2 /g. Further disclosed are processes of producing these nanosized aluminum oxide rod-shaped particles. The aluminum oxide particles as disclosed herein with moderate aspect ratios provide significant advantages as catalyst supports due to their increased surface area, improved mass transfer, excellent thermal stability, and high mechanical strength.

What is claimed is: 
     
         1 . A composition comprising nanosized aluminum oxide particles, wherein the particles have an average particle length of about 50 nm to about 10 μm, an aspect ratio of about 12 to about 25, and a BET surface area of about 10 m 2 /g to about 200 m 2 /g. 
     
     
         2 . The composition of  claim 1 , wherein the aluminum oxide is δ-alumina, γ-alumina, or boehmite. 
     
     
         3 . The composition of  claim 2 , wherein the aluminum oxide is δ-alumina and the composition has a Loss on Ignition (LOI) of about 0.2% to about 8%. 
     
     
         4 . The composition of  claim 2 , wherein the aluminum oxide is γ-alumina and the composition has a Loss on Ignition (LOI) of about 0.2% to about 15%. 
     
     
         5 . The composition of  claim 2 , wherein the aluminum oxide is boehmite and the composition has a Loss on Ignition (LOI) of about 0.2% to about 30%. 
     
     
         6 . The composition of  claim 1 , wherein the aluminum oxide particles are crystalline. 
     
     
         7 . The composition of  claim 1 , wherein the average particle length is from about 0.2 μm to about 4 μm. 
     
     
         8 . The composition of  claim 1 or 7 , wherein the particles have a particle width of about 10 nm to about 250 nm. 
     
     
         9 . The composition of  claim 1, 7, or 8 , wherein the particles have an aspect ratio of about 15 to about 22. 
     
     
         10 . A process of producing aluminum oxide nanorod particles comprising:
 (a) dissolving an aluminum precursor, precipitant, and optionally a polymeric additive in water to provide a solution, wherein the aluminum precursor is an aluminum nitrate, an aluminum chloride, or mixture thereof and the precipitant is selected from the group consisting of urea, NaOH, KOH, NH 3 ·H 2 O, and mixtures thereof;   (b) mixing the solution;   (c) hydrothermally reacting the solution at a temperature of about 80° C. to about 200° C. for about 1 hour to about 24 hours to create a slurry;   (d) collecting precipitates from the slurry; and   (e) calcining the precipitates at a temperature of about 500° C. to about 1000° C. for about 1 hour to about 6 hours to provide the aluminum oxide nanorod particles having an average particle length of about 50 nm to about 10 μm and an aspect ratio of about 12 to about 25.   
     
     
         11 . The process of  claim 10 , wherein the Al 3+  concentration of the solution of step (b) is about 0.1 M to about 1.0 M. 
     
     
         12 . The process of  claim 10 , wherein in step (a) an aluminum precursor and precipitant are dissolved in water to provide the solution and the precipitant is urea. 
     
     
         13 . The process of  claim 10 , wherein in step (a) an aluminum precursor, precipitant, and polymeric additive are dissolved in water to provide the solution and the polymeric additive is selected from a group consisting of cetrimonium bromide, cetrimonium chloride, sodium dodecyl sulfate, polyethylene glycol and mixtures thereof. 
     
     
         14 . The process of  claim 13 , wherein the polymeric additive is sodium dodecyl sulfate or cetrimonium bromide and the precipitant is urea. 
     
     
         15 . The process of  claim 10 , wherein the aluminum precursor is Al(NO 3 ) 3 ·9H 2 O with an oxide content of about 13.4% or is AlCl 3 ·6H 2 O with an oxide content of about 21.1%. 
     
     
         16 . The process of  claim 10 or 15 , wherein the aluminum precursor is dissolved in a concentration of about 1 g/10 mL to about 5 g/10 mL. 
     
     
         17 . The process of  claim 10 or 15 , wherein the precipitant is dissolved in a concentration of about 1 g/10 mL to 6 g/10 mL. 
     
     
         18 . The process of  claim 10 , wherein in step (b) the solution is mixed by stirring for about 30 mins to about 12 hours. 
     
     
         19 . The process of  claim 10 , wherein in step (b) the solution is mixed by sonication and then stirring. 
     
     
         20 . The process of  claim 10 , further comprising aging the slurry of step (c) in deionized water or ethanol prior to collecting the precipitates in step (d). 
     
     
         21 . The process of  claim 10 or 20 , further comprising washing the precipitates of step (d) with deionized water to a conductivity of less than about 100 μS/cm prior to calcining. 
     
     
         22 . The process of  claim 10, 20, or 21 , further comprising dewatering the precipitates of step (d). 
     
     
         23 . The process of  claim 22 , wherein the precipitates are dewatered with ethanol and the process further comprises drying the precipitants at about 50° C. to about 100° C. for about 3 hours to about 12 hours after dewatering and before calcining. 
     
     
         24 . The process of any one of  claim 10 or 20-23 , wherein in step (d) the precipitates are collected by centrifugation. 
     
     
         25 . Aluminum oxide nanorod particles made by the process of any one of  claims 10-24 .